Three common congenital cardiac defects are being studied: aortic stenosis, pulmonic stenosis and ventricular septal defect. In the realm of each one of these anomalies the study has three separate objectives: (1) To provide means of predicting clinical outlook for any patient with such an anomaly, treated medically or surgically, the prediction being individualized according to age, cardiac catheterization data, electrocardiographic and x-ray findings, and clinical symptoms and signs. (2) To provide basis for evaluating the advisability of surgery in cases where the comparative merits of medical and surgical treatment are currently in doubt. (3) To provide means of assessing important hemodynamic quantities indirectly, i.e., without cardiac catheterization. Such assessment would be based jointly on electrocardiogram, roentgenogram, symptoms and signs, host characteristics, and past data on the patient.